Contact lenses, particularly soft contact lenses, are generally manufactured in automated production processes well-known in the art. Depending on the lens forming materials used and also depending on the method of manufacturing, the contact lenses have to be immersed in various liquids such as extraction liquids, rinsing liquids, coating liquids, etc., to obtain the final contact lens which is suitable to be worn in direct contact with the wearer's eye. For that purpose, it is known to transport the contact lenses through several baths containing such liquids. For example, the contact lenses are introduced into containers arranged in a transport carrier which is moved along the length of the individual baths such that the contact lenses contained in the respective containers are exposed to the liquids of the respective baths. For example, after having been transported through one liquid bath the containers arranged in the transport carrier are transferred to a further liquid bath containing a further liquid. By way of example, the liquid baths may serve for lens rinsing, extraction, or coating purposes and may contain either the same kind of liquid, if necessary in different concentrations, or may contain liquids of different kind which are used for different purposes (see above).
US 2011/091642 A1 describes a method and apparatus for transporting contact lenses accommodated in respective containers through successively arranged treatment baths comprising an automatically operating transfer means for transferring the carriers from one dipping bath to the next dipping bath along the travel path.
US 2011/0089053 A1 discloses a container for the accommodation of a contact lens during lens treatment processes such as extraction and/or rinsing and/or coating processes. The container may either be molded in one piece or may comprise several individual pieces which are assembled to form a container. The container generally comprises an elongated tubular body and, at a distal and of the container, a bottom which protrudes convexly towards the outside of the container. The bottom is provided with a number of apertures which enable a flow of liquid into and out of the tubular body.
Once the container has reached the end of the respective bath, the container is lifted out of the liquid of the liquid bath for being transferred into the liquid of the subsequent liquid bath, or for being transferred to another subsequent processing station. During this transfer, liquid of the preceding liquid bath may remain adhered to the surface of the bottom of the container and on the contact lens itself accommodated in the container, and such liquid may either be carried over to the subsequent liquid bath or may be spilled in the production area. In case the container is transferred to a subsequent liquid bath, the corresponding liquid in the said subsequent liquid bath either may be of the same kind but may have a concentration that differs from the concentration of the liquid contained in the preceding bath, or the subsequent bath may contain a liquid of a different kind. Accordingly, the carry-over of liquid from the preceding bath may either change the concentration of the liquid in the subsequent liquid bath or may contaminate the liquid in the subsequent liquid bath. In the first case (subsequent liquid bath contains the same kind of liquid at different concentration), the concentration of the liquid of the subsequent liquid bath must be monitored and may have to be maintained through the addition of fresh liquid or through the addition of one or more of the constituents of the liquid. In the other case (subsequent liquid bath contains different kind of liquid), the liquid of the subsequent liquid bath may have to undergo complex purification or may have to be replaced in case the concentration of the “contaminant” in the subsequent liquid bath exceeds a predefined threshold concentration.
For example, prior to immersing the contact lenses in an extraction liquid, they are rinsed in a water bath. The rinsing of the contact lenses in water prevents or reduces the soiling of the extraction liquid. However, as the containers containing the contact lenses are transferred from the water bath to the extraction liquid bath, small amounts of water are carried over from the water bath to the extraction liquid bath. As a consequence, during the production of contact lenses the concentration of the extraction liquid bath is constantly reduced, so that after a certain time the extraction liquid bath must be purified or the “contaminated” extraction liquid must be replaced with fresh extraction liquid.
It is therefore an object of the invention to further improve the efficiency of the treatment of ophthalmic lenses such as contact lenses, in particular soft contact lenses, in liquid baths.